Magnetoresistive Random Access Memory (MRAM) is a nonvolatile memory technology that uses magnetic polarization to store data, in contrast to other RAM technologies that use electronic charges to store data. One primary benefit of MRAM is that it retains the stored data in the absence of applied system power, thus, it is a nonvolatile memory. Generally, MRAM includes a large number of magnetic cells formed on a semiconductor substrate, where each cell represents one data bit. Information is written to a cell by changing the magnetization direction of the magnetic free layer within the cell, and a bit is read by measuring the resistance of the cell (low resistance typically represents a “0” bit and high resistance typically represents a “1” bit).
An MRAM device generally includes an array of cells that are interconnected using conductive bit lines, conductive digit lines, and/or local interconnects and the like. Practical MRAM devices are fabricated using known semiconductor process technologies. For example, the bit and digit lines are formed from different metal layers, which are separated by one or more insulating and/or additional metal layers. Conventional fabrication processes allow distinct MRAM devices to be easily fabricated on a substrate.
Smart power integrated circuits are single-chip devices capable of managing and providing operating power in a controlled and intelligent manner. Smart power integrated circuits typically include one or more active circuit components, such as, a power circuit component, an analog control component, and/or a digital logic component. Smart power integrated circuits may also include one or more sensors which can be used to measure or detect physical parameters such as position, motion, force, acceleration, temperature, pressure and so forth. Such sensors can be used, for example, to control the output power in response to changing operating conditions. For example, in cell phones, smart power products can be engineered to regulate power consumption, amplify audio signals, and supply power to color screens. In inkjet printers, smart power products can help drive the motors and fire the nozzles for ink delivery. In automobiles, smart power products can help control engine and braking systems, airbag deployments, and seat positioning. Smart power products can also be implemented in a wide variety of other applications.
For integrated circuits (IC's) pressure sensing is an important element of IC design to provide an integrated solution for sensors and circuits. Existing pressure sensors for measuring the pressure suffer from various limitations. For example, many pressure sensing devices consume valuable semiconductor layout area or space. Other limitations of such sensing devices include, for example, excessive size/weight, inadequate measurement precision of the pressure experienced by the pressure sensor, inadequate sensitivity and/or dynamic range, high cost and limited reliability among other limitations.
Micro-Electrical Mechanical Systems (MEMS) integrate mechanical elements, sensors, actuators, and electronics on a common silicon substrate through microfabrication technology. MEMS convert a physical input into an electrical output signal. Typical types of MEMS devices are made of piezoresistive devices or capacitive devices. Resistance of a piezoresistor changes when it the piezoresistor is bent or strained. A piezoresistor can be used to create a piezoresistive pressure sensor which consists of a silicon diaphragm integrated in a silicon substrate. The sensitivity of MEMS based pressure sensors to subtle pressure variations is somewhat limited since the changes in pressure required to register a change in output are relatively large. Moreover, because such piezoresistive pressure sensors are typically integrated in a silicon substrate they tend to consume valuable silicon substrate space.
The miniaturization of many modern applications make it desirable to shrink the physical size of electronic devices, integrate multiple components or devices into a single chip, and/or improve circuit layout efficiency. Ideally, sensors should be manufactured in a cost effective manner which reduces the additional layout area or space the sensors consumes. It would be desirable to have a semiconductor-based device which includes, for example, a MRAM architecture integrated with a smart power architecture including sensor components on a single substrate, particularly where the MRAM architecture, sensor components and the smart power architecture are fabricated using the same process technology. Thus, there continues to be a need for improved pressure sensors.
Accordingly, it is desirable to provide an improved pressure sensor and method, adaptable for measuring or sensing pressure experienced by the pressure sensor. It is further desirable that the improved pressure sensor and method generates an electrical signal that can be converted to a pressure experienced by the pressure sensor. It would be desirable to provide pressure sensors that can be easily integrated with semiconductor devices and integrated circuits (e.g., pressure sensors which are compatible with semiconductor device and integrated circuit structures and fabrication methods). For example, it would be very desirable to provide pressure sensors which exhibit precision measurement and improved measurement performance and which can be integrated in a three-dimensional architecture to conserve lay out area and allow for processing in a cost effective manner. Other desirable features and characteristics of the invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.